In my opinion, the closest you’ll get to a “foolproof” team is one that removes as much randomness as possible from the inherent game RNG. That means:
Board control in the form of universal converters ( not creators or exploders);
Giving up the turn on your terms (baiting with skulls, ideally with a mitigating or throwaway troop in the first slot);
No either-or mechanics in any primary troop spell effect.
The closest I’ve seen to foolproof at endgame is Mercy / Alchemist / Hellcat / Gard’s Avatar, although I’m quite happy with my Forest Guardian team; it’s a skull-spam team that works around most of the typical “gotchas” of skull spam teams.
@KrudlerTheHorse has also published a resilient control team you might be interested in trying: